feat(rules): scale healing spells with caster level

PF1e (SRD spells/cure-light-wounds.md): 'cures 1d8 points of damage +1
point per caster level (maximum +5)'; (spells/cure-moderate-wounds.md):
'cures 2d8 points of damage +1 point per caster level (maximum +10)'.
A HealEffect now carries the same DamageFlatScaling spec as damage
effects (S1b) and resolves it through effective_formula(caster_level)
at cast time, so the flat bonus grows with the caster and stops at the
stated cap. The engine passes the caster's level into _apply_heal_effect
(required keyword: no silent level-0 under-heal); Maximize Spell
maximizes the scaled formula. Cure Light/Moderate Wounds ship the SRD
values; inflict_light_wounds already carried its scaling_flat.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/pf1e_simulator/spells.py

@@ -182,6 +182,27 @@ class ConditionEffect:
 @dataclass(frozen=True)
 class HealEffect:
     formula: DiceExpr
+    # PF1e caster-level scaling for healing (SRD spells/cure-light-wounds.md:
+    # "cures 1d8 points of damage +1 point per caster level (maximum +5)" and
+    # cure-moderate-wounds.md: "cures 2d8 points of damage +1 point per caster
+    # level (maximum +10)"). Absent = level-independent healing, the pre-S5b
+    # behaviour.
+    scaling_flat: DamageFlatScaling | None = None
+
+    def effective_formula(self, caster_level: int) -> DiceExpr:
+        """The healing formula resolved for a caster of ``caster_level``.
+
+        PF1e (CRB, Magic — Caster Level): the flat bonus grows with the caster
+        and stops at the stated cap — bonus = min(max, (level // per_levels)
+        * amount), mirroring ``DamageEffect.effective_formula``.
+        """
+        bonus = self.formula.bonus
+        if self.scaling_flat is not None:
+            bonus += min(
+                self.scaling_flat.max_amount,
+                (caster_level // self.scaling_flat.per_levels) * self.scaling_flat.amount,
+            )
+        return DiceExpr(count=self.formula.count, sides=self.formula.sides, bonus=bonus)
 
 
 @dataclass(frozen=True)
@@ -529,8 +550,11 @@ def _parse_effect(data: Json) -> SpellEffect:
             save_partial=save_partial,
         )
     if effect_type == "heal":
+        flat_raw = effect.get("scaling_flat")
+        scaling_flat = None if flat_raw is None else _parse_flat_scaling(flat_raw)
         return HealEffect(
             formula=parse_dice(_as_str(effect["formula"])),
+            scaling_flat=scaling_flat,
         )
     if effect_type == "buff":
         return BuffEffect(